Stoker for furnaces



Sept, 1944- G. A. KOHOUT I STQKER FOR FURNACES Filed July 26, 1941 4 Sheets-Sheet 1 Sept. 12, 1944. KOHOUT 2,357,899

STOKER FOR FURNACES Filed July 26, 1941 4 Sheets-Sheet 2 III H J6, 61207196 CZfi/wut 4 Sept. 12, 1944. OHOU 2,357,899

STOKER FOR FURNACES' Filed .July 26, 1941 4 Sheets-Sheet 3 s George Q. fi/aui S p 2, 1944. G. A. KOHOUT 2,357,899

STOKER FOR FURNACES Filed July 26, 1941 4 Sheets-Sheet 4 Patented Sept. 12, 1944 I UNITED STATES PATzE-N T OFFICE STOKER FOR George A.Kohout,"hicago,.'lll. Application 3111 26, 1941, iseizia'lE'No. 404,131

Claims. (Cl. 110-105 The present invention relates to stokers for furnaces and more particularly to stokers of the type wherein coal is fed from alargehopper by a plurality of feed screws to the interior of the furnace and then sprayed by means of a fluid blast into-the combustion chamberof the furnace. The construction is such that the coal is 'fed through individual housings by the feed screws to an inclined, expanding outlet at the furnace end of .the screw housing. The coal then rolls down the inclines of the screw housings and is struck byan-air stream which blows the coal dust and small particles away from the larger particles of coal. The air stream also gives an added impetus to the larger particles of coal so that these particles are sprayed out into the furnace and spread along the length of the grate according to the weight and size of each piece. Thecoal particles, when they :pass .downwardly through the air stream, strike a spreader plate and reboundsoas to get the full effect of the air stream.

It is th principal purpose of this invention to provide improvements in the feed screw housings and the associated air delivery and spreader plate constructions whereby to cause 'a device of this character to function more efficiently over a wide range of coal capacity and to avoid difficulty due to coal packing or coking in the outlet of the screw housing.

More specifically it is a purpose of this invention to provide a fuel feeding unit embodying feed screws and feed screw housings wherein the housings are constructed to be substantially D-' shaped in cross section throughout and beyond the length of the screw with an inclined outlet portion on each of the screw housings extending downwardly from the furnace end of the screw and toward the combustion chamber of the furnace at such an angle as to bring the upper'edge of the outlet at the furnace end slightly above or at the level of the screw axis. The inclined outlet desirably is tapered or expanded "toward the combustion chamber, thus providing adequaterelease of the coal to prevent it from co'ln'ng and sticking in the outlet.

The invention contemplates a construction of screw and housing wherein the housing has interior dimensions substantially larger than the screw diameter and wherein the screw .rests loosely on the floor of the housing so that large particles of coal, etc. that enter the housing can work along the top of the screw and be carried to the discharge end of the housing.

Other and more detailed objects and advantages of the invention will appear from. the following description, reference being had to the accompanying drawings wherein a preferred form or-the invention is shown. Itisto be understood however that the drawings and description are illustrative only and are'notto be taken as limiting the invention except insofar as it is limited by the claims.

In the drawings:

.Fig. 1 is a view in frontelevation of a furnace embodying the invention, the 'fuel hopper -and the feed screw "driving mechanism being cut away .to illustrate the inlet to the feed screw housings;

Fig. 2 isa sectional vi'ew'taken on the line'22 of Fig. '1;

Fig. '3 is a view taken substantially on the line 133 of Fig. 2 with certain parts broken away "to illustrate the outlet ends of the feed screw housings;

Fig. 4 is .a fragmentary sectional view taken substantially on the :line 4-4 of Fig. 1;

Fig. :5 is :a fragmentary plan sectional view taken substantially along the line 5-5 of Fig. 1,

certain parts being left out for the sake of clearness;

6 is Ta fragmentary perspective view of a portion of a feed screw housing embodied'in the present invention;

Fig. 7 is a perspective view of a filler block which is utilized between adjacent housings for spacing them;

Fig. 8 is aperspective view of a plate which is utilized to support the inner ends of the air nozzles and to provide a shelf from which the coal fed to the furnace will rebound; and

Fig. '9 is a fragmentary sectional view through the inner or furnace end of a feed screw housing and its associated blast plate, this form. being slightly modified in comparison with the main form of the invention.

Referring now in detail to the drawings, and particularly to Figs. 1 and 2, the present invention is embodied in a furnace having a combustion chamber IQ beneath which there are grates I. The front of the furnace is illustrated in Fig. 1, the entire front being covered by a sheet metal plate l2. Overfire doors l3 and 14 are provided at the front of the furnace and ash pit doors l5 and H5 'arelocated just below the overfire doors. At the left of the furnace as :shown'in Fig. 1 there is provided a fan housing 11, the outlet 18 of which (see Fig. '2) opens into a spreading chamber i9 so as tosupply air under pressur beneath the grates H. A motor '20 drives a fan (not shown) in the fan housing 11.

An air duct 21 extends across the front of the furnace.

'of 'the channel '42.

a {nozzle 48.

flared outwardly as indicated at 52.

fan 23 of the centrifugal type is mounted (see Fig. 4). A motor 24 drives the fan 23. This motor is suspended from the "furnace by means of a bracket 25. V

A coal hopper 26 is mounted at the front of This hopper comprises a bottom portion made up of two channel irons 21 and 28 which extend across the front of the furnace; two end walls 29 and 30,'and front panels 3|, 32 and 33, the front panels and end walls being secured together in any suitable fashion. A 003.1 agitator 34 ismounted in the hopper 26. The hopper also has therein a plurality of feed screws 35, There may be any desired number of feed screws, depending upon the width of the furnace.

In the present instance I have shown four such feed screws. The feed screws are connected as shown best in Fig.2 to drive shafts 36, which shafts are driven intermittently by a pawl 31 and a ratchet wheel 38. The details of the pawl and ratchet mechanism are shown more clearly the screws. are rotated.

The feed screws 35 extend from the hopper into feed screw housings 40. One end of each feed screw housing includes a plate 4| which extends over the channel irons 21 and 28 so as to be supported thereby. Connection is made between the feed screw housings and the front plate I2 of the furnace .by means of va channel 42 on each housing (see Fig. and a lock plate 43 that drops down into the channel in front of the plate I2, the plate l2 of course being provided with an aperture big enough to permit passage of flanges 44 and 4-5 on opposite sides The housing 40 comprises a casting and the screw receiving passage 40a therein is substantially D-shaped in cross section as'shown clearly in Fig. 6. This passage 40a is substantially larger than the screw diameter; for

example, 5 inches horizontally and vertically for 'may pass through the housing without sticking and breaking the shear pins for the screw. 7

The inner'or furnace end of the housing 40 includes a portion 46 substantially rectangular in cross section and below the feed screw opening.

This rectangular hollow portion 46 is adapted to receive and. support a blast plate 41 and a fluid The fluid nozzle 48 extends through an opening 49 in the front furnace wall l2 and is connected to the'air duct 2| through an opening 50 in the top of the air duct. Individually adjustable valves 5| are provided in the nozzles 48 so as to control the supply of air thereto.

a The passage 40a extends to the end of the feed screw 35 and from about the end of the feed screw it is directed angularly downward and is The top wall 53 of the outlet portion 52 extends downer angle than the top wa1153. It is much shorter.

The sidewalls 55 and 56 (see Figs. 3 and 5) may be forced into the hollow space by a fan.

also flare outwardly toward the furnace combustion chamber so as to provide an expandin outlet from the end of the feed screw 35 to the combustion chamber. The fact that the outlet 52 expands and extends angularly downward into the combustion chamber prevents fuel from coking in front of the screw and enables the coal to roll freely from the front end'of the screw down the inclined wall 54 across the outlet end of the nozzle 48 onto the plate 41.

The plate 41 is shown in perspective in Fig. 8. This plate has two rearwardly extending portions 51 and 58, which portions are provided with depending lugs 59 and 60 that are adapted to hook over the back of the part 46. At the front end the plate 41 has an enlarged portion 6| that extends down in front of the part 46. The portion 6| is provided with a plurality of channels 62 so that air may be fed by natural draft through these channels into the combustion chamber. The air of course enters from the front of the furnace through the openings 49 or it Since the blast plate is subject to the heat of the furnace this air inlet provision is important in keeping the temperature of the blast plate down. However, it is a simple matter to replace a blast plate if it is damaged byheat or when it becomes worn by the action of the coal falling thereon and rebounding therefrom. It will be noted that the plate 41 has a flat top surface 64 and a steeply inclined front surface 65. The nozzles 48 direct their blast outwardly in a flaringstream across the surface 64, The flaring outlet of the nozzles 48 is shown best at 66 in Fig. 5 where it will be seen that this flaring outlet follows the flare of the Walls 61 and 68 at the side edges of the surface 64. g

The front furnace wall is constructed of the wall 10 which serves to support theinner end of the several housings 40, the portions 46 of the housings resting directly uponthe refractory wall 10. 'Above the housings there is an air space H extending across the front of the furnace. through a side opening 12 in the furnace. air in fact may come from the air passages that are commonly provided in the side walls of fur-, naces fo cooling the sidewalls. Above the air space H the refractory material indicated at" V completes the front furnace wall. This upper refractory material is supported by an I-beam 14 and a metal plate 15. p

In order to protect the inner ends of the housings 40 from the direct heat of thefurnace I provide castings 16; which castings are adapted to fit on and be supported by an upwardlyextending flange 71 on each of the housings 40. The castings I6 have flanges 18 upon which arch tile 19 is hung. The arch tile is slotted so as v to receive the flanges 18. It will be noted from r r Fig. 3 that there are two flanges 18 on, each 'vide means for closingthe space between. the

housings. This means comprises castingsofthe.

This air space is adapted to receive air This type illustrated in perspective in Fig. 7. These castings 83 have top flanges 84 cooperating with the flanges H to support the castings 16. The castings 83 also have laterally extending lugs 85, 86, 81 and 88, which lugs are adapted to engage behind the flanges 11 at the sides of the inner ends of the housings 40. In order to aid in keeping the castings cool and in furnishing air for combustionpurposes these castings preferably are provided with air passages 89 and 99.

It is believed to be evident from an inspection of Figs. 3, 5, 6 and 7 how the castings 83 are interlocked with the housings 49.

Referring now to Fig. 9, in this form of the invention a slight modification has been made which in certain instances is desirable for the protection of the feed screws 35. This modification consists in providing a pivoted door 9| at the junction of the passage 40a with the outwardly flaring, downwardly inclined outlet passage 52. The door 9| is hung on a pin 92 that is pivoted in a recess 93 provided in the housing 40. Normally when coal is being fed by the screw 35 the door 9| will be pushed open by the coal just sufficient to allow it to fall. When the coal feed is shut off the door 9| falls down by its own weight to prevent the radiant heat from the combustion chamber reaching the'screw 35. In most installations the door 9| is not necessary. From the foregoing description it is believed that the construction and advantages of a stoker embodying my invention will be readily apparent to those skilled in this art. Having thus described my invention, what I- claim as new and desire to secure by Letters Patent is:

l. A stoker for furnaces'comprising a hopper,-

feed screws in the bottom of the hopper, means to drive said screws, horizontally extending feed screw housing tubes projecting from the hopper for feeding and delivering fuel into the furnace, said tubes being D-shaped in cross section and having outlet openings extending angularly downward from the screw ends, the most forward portion of the top of the outlet openings being about the level of the axis line of the screws, the side walls of said outlet openings diverging to the discharge ends of the openings and the bottom walls of the outlet openings being directed downwardly towardthe discharge ends at a greater angle to the horizontal than the top walls of the outlet openings.

2. A stoker for furnaces comprising a hopper, feed screws in the bottom of the hopper, means to drive said screws, horizontally extending feed screw housing tubes projecting from the hopper for feeding and delivering fuel into the furnace, said tubes being D'-shaped in cross section and having outlet openings extending angularly downward from the screw ends, the most forward portion of the top 'of the outlet openings being about the level of the axis line of the screws, the side walls'of said outlet openings diverging to the discharge endsof the openings and the bottom walls of the outlet openings being directed downwardly toward the'discharge ends at a greater angle to the horizontal than the top walls of the outlet openings, said housing tubes being substantially larger in vertical depth than the diameter of the screws therein.

3. A stoker for furnaces comprising a hopper, feed screws in the bottom of the hopper, means to drive said screws, horizontally extending feed screw housing tubes projecting from the hopper for feeding and delivering fuel into the furnace, said tubes being D-shaped in cross section and having outwardly flaring outlet openings extending angularly downward from the screw ends, the most forward portion of the top of the outlet openings being about the level of the axis line of the screws, and the side and bottom walls of said outlet openings flaring outwardly and downwardly, said tubes having integral rectangular portions below the outlet ends thereof adapted to support the outlet ends of the tubes, and air nozzles extending through said rectangular portions and terminating at the lower edges of the bottom walls of said outlet openings,

4. A stoker for furnaces comprising a hopper, feed screws in the bottom of the hopper, means to drive said screws, horizontally extending feed screw housing tubes projecting from the hopper for feeding and delivering fuel into the furnace,

said tubes being D-shaped in cross section and having outwardly flaring outlet openings extending angularly downward from the screw ends, said tubes also having integral hollow supports below the outlet ends thereof supporting the outlet ends of the tubes, a blast plate extending through each hollow support and removably mounted therein below the outlet end of the tube, and an'air nozzle extending into each hollow support over the blast plate. L

5. A stoker for furnaces, comprising a hopper,

feed screws extending across the bottom of the hopper, drive means at one side of the hopper to which said screws are attached, and feed screw housings mounted on the opposite side of the'hopper'and extending from it, said housings having substantially D-shaped passages therein substantially larger than the feed screw diameters and said feed screws extending into said passages and resting on the floors thereof, the said housings having angularly, downwardly directed outer ends that expand from the ends of the feed screws outwardly, the roofs of the hous ing passages at the extreme outer ends thereof being at least as high as the screw axes.

GEORGE A. KOI-IOUT. 

